Devices commonly referred to as “drain inlet inserts” or “catch basin inserts” now find increasing use as a Best Management Practice (BMP) to meet the compliance requirements of environmental regulations which mandate that on new developments or construction modifications above a specified size, certain contaminants, such as Trash, Total Suspended Solids (TSS) or Total Oil & Grease (TOG) should not be discharged post-development in concentrations exceeding pre-development levels. Devices are generally available to satisfy the requirements for trash discharge control, but control of smaller, more complex suspended solids and hydrocarbon-based contaminants require equipment that is more complex and expensive, so much so, that the trend for some time has been for property developers to use drain inlet inserts which can be fitted into even the smallest sizes of drain inlet vaults. Examples of such inserts are disclosed by Abtech (U.S. Pat. No. 6,344,519), DrainPac (U.S. Pat. No. 6,562,233), and Fossil Filter (U.S. Pat. Nos. 5,720,574; 5,744,048; 5,958,226; 6,080,307; 6,099,723). These inserts can be efficient for trash removal and less so for smaller sizes of TSS particulate or TOG, but they are less expensive, readily available, and since standards for acceptability of such BMP's have not yet been fully promulgated or adopted, are not prohibited by many city/county plan check functions. Devices most efficient for capture of contaminants will be those that function as a gravity clarifier, allowing TSS to settle to the bottom of a water-detaining container and TOG to float to the surface of water standing in such a container where it can be collected by a hydrocarbon sorbent media. Providing these capabilities is not only more expensive, but also introduces an additional problem which is beginning to limit use of the most efficient hydraulic drain inlet insert devices, such as the Hydro-Cartridge (U.S. Pat. No. 5,297,367). Namely, the problem of such standing water providing an environment for mosquito growth. Now that West Nile Virus has been identified across the country as a serous potential health hazard, Vector Control Agencies are actively discouraging the use of drain inlet vault inserts which operate with standing water.